Occationally, Pachyderm introduces changes that are
backward-incompatible: repos/commits/files created on an old version of
Pachyderm may be unusable on a new version of Pachyderm. When that
happens, we try our best to write a migration script that “upgrades”
your data so it’s usable by the new version of Pachyderm.

To upgrade from version X to version Y, look under the directory named
migration/X-Y. For instance, to upgrade from 1.2.2 to 1.2.3, look under
migration/1.2.2-1.2.3.

It’s paramount that you backup your data before running a migration
script. While we’ve tested the scripts extensively, it’s still possible
that they contain bugs, or that you accidentally use them in a wrong
way.

In general, there are two data storage systems that you might consider
backing up: the metadata storage and the data storage. Not all migration
scripts touch both systems, so you might only need to back up one of
them. Look at the README for a particular migration script for details.